1. Field of the Invention
The present invention relates to an integrable, high frequency, wide bandwidth superlinear amplifier and the method of its fabrication. More specifically, the invention is addressed to a high frequency, wide bandwidth, high stability, low noise, high reliability and large negative feedback amplification system which is fabricated with a view toward improving the integration capabilities.
2. Discussion of Background
Prior art attempts to improve the performance of high frequency, wide bandwidth, superlinear amplifiers have generally dealt with the increase in feedback or deep feedback. This technique utilized in the prior art provides two serious problems. In a first instance the design for a high frequency and deep feedback amplifier has an increasing amount of complexity. For example, a line amplifier having a bandwidth of from 0.3 MHz to 9 MHz has more than 50 "K" correcting elements when the standard Bode method is utilized. Because of the large number of elements, it is not possible to make the parameters of the elements completely consistent with each other and it is also difficult to control any parasitic effects of the parameters. It is also a requirement of this type of structure to require precise elements and therefore for these reasons it is difficult to integrate an amplifier with high performance into an integrated circuit environment. The second serious problem with the application of deep feedback in order to provide better performance in a high frequency amplifier involves the need for reversed bias isolation in an integrated circuit environment. However, both isolation capacitance and parasitic inductance are very large which makes reverse bias isolation difficult. Therefore, the parasitic parameters are not easily and effectively controlled and an additional phase shift must be considered for use in a high frequency circuit.
The amplifiers discussed above with respect to the prior art are usually fabricated by discrete elements or hybrid integration with thick and thin film techniques. Thus, each amplifier must be carefully designed and adjusted, and the rate of the products which meet this specification in any particular batch is usually less than 10%. Thus it is very difficult to provide for mass fabrication and integration production. Also it is impossible to produce a series and a universal integrated amplifier which is of a high quality or to provide a simple design for such amplifier with high productivity which could be constructed by discrete elements.
If a high frequency (or low frequency) wide band superlinear amplifier could be constructed with simple design, a decreased number of correcting elements for the feedback, and increased stability with respect to independence from the transistor characteristics, a small amount of additional phase shift and less cost in an integrated circuity environment, there would be many applications with respect to amplification for analog signals as well as PAM (Pulse Amplitude Modulation), PCM (Pulse Code Modulation) signals, precise and high speed automation systems, communications systems, military and aerospace equipment as well as audio systems.
To this date there exists no high frequency wide band superlinear universal type integration products having a fabrication method which satisfies and overcomes each of the above disadvantages. U.S. Pat. Nos. 3,774,118; 3,530,392; 2,959,741; and 2,885,494 do not propose any simplified design method for the feedback in the nature of a K.beta. nor have they yielded any new methods of integration. Most particularly none of these references provide for a universal and serialized design and production utilizing discrete and integrated elements.